The project examining the interaction of lipoproteins and thyroid hormones in serum has been continued. In previous work we showed that a brief period of hypothyroidism alters the hormone distribution among the lipoproteins, causing a decrease in VLDL and LDL binding despite a relative increase in VLDL and LDL cholesterol, an increase in HDL binding, and a reversal of T4 and T3 binding to the smallest HDL size subgroup. The present study of three patients with thyroid hormone resistance and largely compensated hypothyroidism showed thyroid hormone distribution that differed markedly from both normal and hypothyroid subjects. The most striking difference was a much lower binding of both T4 and T3 to HDL and a much higher binding to LDL. This might serve as a marker for thyroid hormone resistance if confirmed in a larger group of patients. - thyroid hormones, transport proteins, lipoproteins, thyroid hormone binding, hypothyroidism, thyroid hormone resistance